With leathery, arching stems that arise from an underground rootstock and in winter look like dead sticks stuck in the ground, leatherstem is an unusual plant. It spreads from underground runners to form colonies as wide as 6 feet. The stems are rubbery and tough, flexible enough to be tied in a knot without breaking. The clear to yellowish sap inside turns blood red when exposed to air, hence the name "Sangre de Drago", which means "dragon's blood" in Spanish. The rootstock is up to 3 feet long and orange-colored. The leaves are narrow and clustered on spur branches, and two different leaf shapes distinguish two varieties: those of var. graminea are longer and narrower (and sometimes with 2 or 3 lobes) than the wider, blunter-tipped leaves of var. dioica. Var. graminae grows mainly in the Trans-Pecos and into Mexico, whereas var. dioica is more widespread, found on limestone hills in Central Texas through lower desert areas in the Trans-Pecos to New Mexico. Leatherstems's tiny flowers, white to pink, appear in clusters in spring and early summer. It grows in full sun and well-drained soil, and can be hurt by temperatures under 15 degrees F. The astringent sap was reportedly used by Indians to treat sore gums, and it also makes a dark red dye (which is harmful to cloth).